Prime Minister Justin Trudeau​ says his job is to look out for Canada's best interests and not act as a "cheerleader" for various pipeline projects as the previous Conservative government did.

Trudeau spoke at a news conference following a meeting with Montreal Mayor Denis Coderre. The two discussed a broad range of issues, including the proposed Energy East pipeline.

"My responsibility as prime minister is to make sure that on national projects, we're behaving in a way that both contributes to the economy, to a secure environment, to bringing people together and mostly to creating a better future," Trudeau said in Montreal on Tuesday morning.

It's not up to the federal government to decide in advance what projects it wants to push through, the prime minister said in a shot across the bow of the previous Conservative government.

"For 10 years, we had a government that acted rather as a cheerleader for such projects instead of acting as a responsible referee and establish a clear, open, rigorous and transparent approval process — and that's what we intend to do," Trudeau said in French during a news conference in Montreal.

Trudeau said his government would announce a new review process for pipelines and other energy projects "shortly."

Asked whether the federal government will require new supplementary climate tests for proposed pipelines, Trudeau said the Liberals would bring in new rules requiring companies to "take into account all greenhouse gas emissions including those upstream."

Coderre, who engaged in a public war of words with Saskatchewan Premier Brad Wall after taking a position against the Energy East pipeline last week, stood his ground but appeared to bring the rhetoric down a notch Tuesday.

The proposed Energy East pipeline would carry 1.1 million barrels a day of oilsands crude from northern Alberta across the country through Quebec and on to New Brunswick, where it could be shipped abroad.

"At the end of the day it's all about being respected," Coderre said adding "it's to be responsible and have a balanced approach between economic development and sustainable development and... these cities are playing that role to make sure we can get that."

Coderre said it's not because Montreal and other cities in the province are raising environmental concerns and asking others for due diligence that they "lack respect."

The Montreal mayor said he welcomed the federal government in its role as referee, "as it should be."

Ambrose defends current rules as 'rigorous'

Interim Conservative Party Leader Rona Ambrose on Monday defended the changes her party brought to Canada's environmental review process.

"A lot of people will tell you that it was a very rigorous process," Ambrose said during an interview on CBC News Network's Power & Politics on Monday.

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Ambrose said the longer the new government waits to announce details of a new review process, the more uncertainty it creates leading to investor losing confidence.

She encouraged the government to make changes "as fast as possible so there's certainty in the business community."